UV-YAG laser drilling of glass-reinforced PCB material

The miniaturization of electronic products for information and communication has led to the increase of circuit density of PCBs. This means that the holes which connect the isolated circuit layers in multilayer PCB are downsizing. CO2 and Nd:YAG laser operated at infrared wavelength of 10.6 mm and 1.06 mm are used extensively to fabricate microvias in PCB fabrication. However, the major drawback of laser drilling GFRP materials is the existence of heat-affected zone (HAZ) which are formed around the laser-drilled holes. This is because the material-removal mechanism with infrared lasers is a thermal mechanism (melting, evaporation, or vaporization). The differences in temperatures of vaporization and decomposition between glass fibres and epoxy resin in GFRP materials result in the presence of HAZ, which always show itself as recession and decomposition of matrix material. One of the most important methods to reduce the thermal effects is to use UV lasers in drilling microvias. The high energy UV photons can directly atomize material in a process known as photo-ablation.

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To investigate the characteristics of the heat affected zone (HAZ) of the UV YAG laser drilled hole in glass fibre reinforced plastic (GFRP) printed circuit boards.

The structures of the HAZ produced by different laser parameters were demonstrated.

To understand the forming mechanism of HAZ

To evaluate and qualify the size of HAZ in fibre reinforced composites